Ever since the Wright Brothers' first powered flight in 1903, commercial aircraft have relied on liquid hydrocarbon fuels. However, the need for greenhouse gas emission reductions along with recent progress in battery technology for automobiles has generated strong interest in electric propulsion in aviation. This work provides a first-order assessment of the energy, economic, and environmental implications of all-electric aircraft. We show that batteries with significantly higher specific energy and lower cost, coupled with further reductions of costs and CO 2 intensity of electricity, are necessary for exploiting the full range of economic and environmental benefits provided by all-electric aircraft. A global fleet of all-electric aircraft serving all flights up to a 400-600 nmi (741-1,111 km) distance would demand an equivalent of 0.6-1.7% of worldwide electricity consumption in 2015. Whereas lifecycle CO 2 emissions of all-electric aircraft depend 2 on the power generation mix, all direct combustion emissions and thus direct air pollutants and direct non-CO 2 warming impacts would be eliminated.

Policies aimed at influencing air transportation must operate in a complex, interacting global system of passengers, airlines, airports and other stakeholders. Tools which are capable of assessing policy outcomes in this situation are vital. Given the high uncertainty about future demand, costs and technology characteristics on policy-relevant timescales, such tools also need to allow the evaluation of outcomes from a wide range of plausible futures. This paper presents the validation study and initial baseline results from a comprehensive, open source update of the global AIM aviation systems model. We show that running the model from 2005 to 2015 using 2005 base year data reproduces well the observed demand levels and patterns of growth. Running from a 2015 base year, we project global demand in 2050 of between 13,800 billion and 46,000 billion revenue passenger kilometres (RPK), respectively 2.2 and 7.4 times year 2015 values, depending primarily on the future scenario for population, income and oil price assumed. Absent any radical change in aircraft technology, this would lead to global direct CO2 emissions from aviation of between 876 and 2,500 Mt, or 1.5 to 4.4 times the year-2015 level. This wide level of baseline variation may present a challenge for long-term aviation policy and its adaptability to different futures.

The inherently global, connected nature of aviation means that carbon leakage from aviation policy does not necessarily behave similarly to leakage from other sectors. We model carbon leakage from a range of aviation policy test cases applied to a specific country (the United Kingdom), motivated by a desire to reduce aviation CO2 faster than achievable by currently-planned global mitigation efforts in pursuit of a year-2050 net zero CO2 target. We find that there are two main components to leakage: one related to passenger behaviour, which tends to result in emissions reductions outside the policy area (negative leakage), and one related to airline behaviour, which tends to result in emissions increases outside the policy area (positive leakage). The overall leakage impact of a policy, and whether it is positive or negative, depends on the balance of these two components and the geographic scope used, and varies for different policy types. In our simulations, carbon pricing-type policies were associated with leakage of between +50 and-150% depending on what is assumed about scope and the values of uncertain parameters. Mandatory biofuel use was associated with positive leakage of around 0-40%, and changes in airport landing costs to promote more fuel-efficient aircraft were associated with positive leakage of 50-150%. • Carbon leakage in aviation policy arises from airline responses (typically positive leakage) and passenger responses (typically negative leakage). • Depending on the geographical scope, policy type and values for uncertain parameters, leakage may be between around-150 to +150 %. • Of the policies investigated in this study, leakage was typically most negative for carbon pricing and most positive for environmental landing charges. • Absolute values of leakage are smallest where policies are considered on the basis of all arriving and departing flights.

In this paper we demonstrate the ability of a model, which simulates competition between airlines in a domestic aviation market, to accurately reproduce real world behaviour. The Australian market was chosen as a test case as it is a geographically isolated region with significant demand and complexity, including one of the busiest routes in the world, where connecting international passengers do not significantly skew the market. The model is based on an n-player noncooperative game, where each airline represents a player within the game. The primary assumption is that each airline attempts to maximise profits by adjusting the decision variables of airfares, flight frequency and choice of aircraft on routes within its network. The approach works iteratively, allowing each airline to respond to the decisions made by other airlines during each successive optimisation. The model is said to reach convergence when there is no significant change in any airline's profit from one iteration to the next. Once this occurs, the predictions of each airline's decision variables can be compared to real data. The model gives highly detailed predictions of airline specific airfares, flight frequencies on segments, passenger flows and airline market share, which strongly correlate with observed values.